1919.j The Sixth Indian Science Congress. elxxxv 
basic magmas, owing their present shape and distribution to 
factors pre dating the serpentinisation of such rocks, yet Indian 
geological literature contains suggestions that serpentinisation is 
accompanied by the segregation of chromite, in particular with 
piso to the deposits of Salem and Baluchistan ;! so that 
, perhaps, not out of place to record that the result of a 
pete study in the field of the evidence both in Singhbum and 
Baluchistan? is to show conclusively that in both areas the 
present form of the chromite deposits is the result of primary 
segregation, except where modified by movements due to me- 
chanical causes. That this should be so seems reasonable in 
view of the great chemical stabiiity of chromite as yar vvigeta 
y the formation of the chrome-chert and chrome-marble 
ferred to above, and as is ioken advantage of in faanadtrotoal 
practice when chromite. is used as a neutral refractory mate- 
rial for separating the pee roof from the basic hearth in open- 
hearth steel-furnaces 
C. Epigenetic ore-deposiis due to granitic intrusions. 
Three cases of the probable introduction of valuable ore- 
afte into rocks of ag oie’ age by the intrusion of granitic 
magmas will be referred t 
4) The wolfram, apa ache, -magnetite, copper, uranium, 
argentiferous galena, and gold deposits of Singh- 
(2) The -HabcbenG armhole and blende-galena lodes of 
ikkim. 
(3) The gold lodes of Kolar. 
It is now a generally —— idea that, when a granitic 
age lee 7 ma solidifies, all the surplus con- 
ion rom * 
orate eae aire stituents not required in the formation 
mother- liquor—constituents that were present only in minute 
quantities in the whole mass of the granitic magma being 
often thus soianenbented into this residual fluid. The principal 
constituents of this residtial magma are water, silica, alkalies 
and alumina, often with useful metals such as tin, tungsten, 
commonly chlorine ; but the exact nature of these constituents 
in a given case will naturally depend upon the composition of 
the original magma. 
It is difficult to formulate clear ideas as to the physical 
state of the constituents of this mother-liquor, but it seems 
PQ. Ss, Micidlaarion: fee ge Geol. Surv. Ind., XXIX, p. 33 (1896); 
G. H. Tipper: Zhob Dis: etteer, I, p. 187, (1907). 
2 Rec., G.S.I., XLVI. p. rT 1917). 
